1720128921 has 8 divisors (see below), whose sum is σ = 2621148864. Its totient is φ = 982930800.

The previous prime is 1720128913. The next prime is 1720128929. The reversal of 1720128921 is 1298210271.

It is an interprime number because it is at equal distance from previous prime (1720128913) and next prime (1720128929).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1720128921 - 2³ = 1720128913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1720128929) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 40955430 + ... + 40955471.

It is an arithmetic number, because the mean of its divisors is an integer number (327643608).

Almost surely, 2^1720128921 is an apocalyptic number.

It is an amenable number.

1720128921 is a deficient number, since it is larger than the sum of its proper divisors (901019943).

1720128921 is an equidigital number, since it uses as much as digits as its factorization.

1720128921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 81910911.

The product of its (nonzero) digits is 4032, while the sum is 33.

The square root of 1720128921 is about 41474.4369582035. The cubic root of 1720128921 is about 1198.1752175195.

The spelling of 1720128921 in words is "one billion, seven hundred twenty million, one hundred twenty-eight thousand, nine hundred twenty-one".